Conventionally, semiconductor devices have been miniaturized so that they have large capacity and high integration. However, in the generation of 10 nm design rule, since the difficulty of exposure is bottlenecked, the miniaturization of semiconductor devices has slowed down. Semiconductor manufacturers have provided three-dimensional laminate devices instead of plane devices so as to accomplish large capacity semiconductor devices instead of depending on miniaturization.
Since three-dimensional devices are laminated, their thickness becomes greater than that of conventional devices. Thus, a problem in manufacturing three-dimensional devices is to treat thick laminate structures. Since a treatment aspect ratio (the ratio of a plane size of a hole or a trench and its depth) is greater than that of a conventional structure, an etching treatment for holes or trenches would become very difficult. In addition, techniques for evaluating and inspecting three-dimensional devices are becoming important to improve development turn around time (TAT).
Etching of contact holes is evaluated in such a manner that after an etching rate of a bear wafer is evaluated, etching time is calculated based on the acquired data, and then treatment time is estimated. For etching, an analysis of plasma light emission is performed in real time and a final etching result is analyzed and determined. However, in laminate structures of three-dimensional devices, etching rates depend on individual films. The thickness of each film is as small as around 100 nm. Their final determination for etching treatment would become difficult. Conventionally, when it is determined whether contact holes of a sample are open/not open, since it needs to be fractured so as to analyze its cross-section, TAT would deteriorate.
As an evaluation of a pattern treatment result using an electron microscope technique, PTL 1 discloses a technique, a microstructure of a bottom portion of a hole having a large aspect ratio is analyzed with a substrate current so as to estimate the film thickness of a residual film that is present at the bottom portion of the hole. However, if a pattern is present in a lower layer, it becomes difficult to measure the substrate current and since the thickness of the residual film is limited, this evaluation technique is difficult to be applied to the treatment result evaluation for an etched pattern.